TITLE:   GCN CIRCULAR
NUMBER:  25464
SUBJECT: GRB 190821A: Swift-BAT refined analysis
DATE:    19/08/24 15:57:08 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
A. D'Ai (INAF-IASFPA), H. A. Krimm (NSF),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry
downlink,
we report further analysis of BAT GRB 190821A (trigger #921722)
(D'Ai et al., GCN Circ. 25427).  The BAT ground-calculated position is
RA, Dec = 250.070, -34.027 deg which is
   RA(J2000)  =  16h 40m 16.9s
   Dec(J2000) = -34d 01' 35.5"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 83%.

The mask-weighted light curve shows a multi-peaked structure that starts
at ~T-3 s and ends at ~T+60 s. The highest peak occurs at ~T+30 s.
T90 (15-350 keV) is 57.1 +- 2.6 sec (estimated error including systematics).

The time-averaged spectrum from T-3.3 to T+59.5 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.03 +- 0.10.  The fluence in the 15-150 keV band is 2.4 +- 0.1 x 10^-6
erg/cm2.
The 1-sec peak photon flux measured from T+29.98 sec in the 15-150 keV band
is 2.8 +- 0.3 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/921722/BA/